The lipoxins (LX) are tetraene-containing eicosanoids generated from arachidonic acid via several pathways involving the combined action of various lipoxygenases. (Science 1987, 237, 1171. Angew. Chem. Int. Ed. Engl. 1991, 30, 1100. Curr. Opin. Hematology 1994, 1, 69. Serhan, C. N. Biochim. Biophys. Acta 1994, 1212, 1. Prostaglandins & other Lipid Mediators 2002, 68-69, 433). Two major structural types of LX have been identified, namely LXA4 and LXB4 (Scheme 1). The LX are generated largely transcellulary (e.g. via interactions between epithelial cells and neutrophils). Recent studies by Serhan have shown that, while acetylation of COX-1 by aspirin inhibits prostanoid formation, similar acetylation of COX-2 allows the formation of 15R-HETE, which is converted to 15-epi lipoxins (aspirin-triggered lipoxins) (Scheme 1). (Curr. Opin. Hematology 1994, 1, 69. Serhan, C. N. Biochim. Biophys. Acta 1994, 1212, 1. Prostaglandins & other Lipid Mediators 2002, 68-69, 433).

A key feature of LX that distinguishes them from most other eicosanoid mediators (or modulators) of inflammation is their potent antiinflammatory actions (Prostaglandins 53:107, 1997; Prostaglandins & other Lipid Mediators 68-69:433, 2002). The in vitro and in vivo activities of the best-characterized lipoxin, LXA4, include: (a) inhibition of neutrophil chemotaxis, adherence, and transmigration; (b) suppression of neutrophil activation (including NF-kB activation, superoxide generation and elastase secretion); (c) suppression of IL-8 production by epithelia and leukocytes; (d) upregulation of bactericidal permeability-increasing protein expression in epithelial cells; (e) upregulation of monocyte chemotaxis; (f) upregulation of monocyte ingestion of apoptotic neutrophils (Prostaglandins 53:107, 1997; Prostaglandins & other Lipid Mediators 68-69:433, 2002; Proc Natl Acad Sci USA 99:13266, 2002; Proc Natl Acad Sci USA 99:3902, 2002). In a variety of in vivo models, LX have been shown to prevent neutrophil-mediated damage, and promote the resolution of neutrophil-mediated inflammation (Ernst Schering Res Found Workshop 31:143, 2000; Prostaglandins 53:107, 1997; Prostaglandins & other Lipid Mediators 68-69:433, 2002). Notably, LX analogues have recently been shown to downmodulate allergic pulmonary inflammatory responses in mouse models (Biochemistry 1995, 34, 14609. J. Biol. Chem. 1997, 272, 6972. Proc. Nat. Acad. Sci. 1997, 94, 9967. Nature Immunol 8:1018, 2002. J Immunol 2003 170: 2688).
Several studies have established the facile metabolic deactivation of the lipoxins. As a result, in order to develop biostable analogs of LX, it is important to modify their structures in order to enhance their chemical and in vivo stability. Several biostable LX analogs have been reported. (Biochemistry 1995, 34, 14609).